The District of Columbia—identical with the city of Washington—is the capital of the United States. It is located between Virginia and Maryland on the Potomac River. The district is named after Columbus.

DC history began in 1790 when Congress directed selection of a new capital site, 100 sq mi, along the Potomac. When the site was determined, it included 30.75 sq mi on the Virginia side of the river. In 1846, however, Congress returned that area to Virginia, leaving the 68.25 sq mi ceded by Maryland in 1788. The seat of government was transferred from Philadelphia to Washington on Dec. 1, 1800, and President John Adams became the first resident in the White House.

The city was planned and partly laid out by Maj. Pierre Charles L'Enfant, a French engineer. This work was perfected and completed by Maj. Andrew Ellicott and Benjamin Banneker, a freeborn black man who was an astronomer and mathematician. In 1814, during the War of 1812, a British force burned the capital including the White House.

The District of Columbia was administered by three commissioners appointed by the president, until Nov. 3, 1967 when a mayor-commissioner and a 9-member council, appointed by the president, took office. On May 7, 1974, a Home Rule Charter was approved, giving DC its first elected municipal government in over a century. The district has one nonvoting member in the House of Representatives and an elected Board of Education.

A proposed constitutional amendment, which would give Washington a voting representation in Congress, failed to be ratified by the requisite 38 states. Petition and bills for DC's statehood were introduced in 1983 and 1993 and the district continues its push for statehood.

In December 2009, Mayor Adrian Fenty signed a bill passed by the Council of the District Columbia to legalize same-sex marriage. Marriage licenses for same-sex couples were handed out as of March 3, 2010. With the passing of the bill, Washington DC became the first jurisdiction below the Mason-Dixon Line to legalize same-sex marriage.